The present invention relates, in general, to point-of-use distillation systems, and more particularly to compact, continuous-flow distillers for the purification of drinking water.
The global need for safe drinking water is commonly recognized, for the health problems resulting from chemicals, bacteria and viruses in drinking water has been well documented. Many products, including water distillation devices, have been developed in attempts to provide safe water for drinking, but problems still exist. For example, reverse osmosis (RO) point of use water purification systems have limited and unsustainable contaminant removal, can allow the formation of biofilm on filter membranes, and produce waste water. Research has shown that biofilming can be reduced by timely and critical maintenance, but it cannot be completely eliminated and backflushing may contaminate the system. Ultraviolet (UV) water purification systems only address the problem of microbial contamination, and do not remove other contaminants from water. Furthermore, changing turbidity conditions in the water reduces the ability of such systems to kill microbes. Distillation is the oldest and most reliable technology for point of use water purification, for it is reliable, sustainable, and removes a greater percentage of contaminants from water than any other technology. However, difficulties have been encountered in the development of acceptable point of use distillers, and these problems have prevented their widespread use.
A common problem in prior art distillers is the difficulty involved in properly cleaning the boiler, for it usually is difficult to get to the boiler and difficult to clean scale from its interior. The buildup of scale in the boiler tanks of distillers is partially due to the fact that untreated influent water contains bicarbonate ions which will initially break down into carbonate ions, causing the formation of scale. This problem can be reduced by preconditioning or softening the influent water and by preheating influent water prior to entering the boiler. Partial, instead of complete, draining of the boiler can also reduce scale buildup, but periodic cleaning is still required and the construction of most prior distillers have made the cleaning process so complicated that the distiller gradually becomes less efficient.
Although numerous attempts have been made to facilitate the descaling and cleaning of distillers, the problem has not been completely solved, for most such attempts have resulted in additional plumbing requirements or additional components, which increase the cost of purchasing and maintaining the units. For example, some distillers have water cooled condensers which produce waste water and some have periodic automatic draining of the boiler, but these still do not reduce scale buildup or eliminate the difficulties of cleaning.
Proper cleaning of a typical vapor generating distiller apparatus requires substantial time, labor and prolonged periods of operational downtime. In some cases, cleaning may include introduction of cleaning agents into the apparatus and leaving these agents in place for a period of time. Not only does this require long periods of downtime, but it may also be an unwanted source of pollution and contamination of the distilling apparatus.
Increasingly, another concern about the use of distilling devices is their poor energy efficiency. In order to provide an energy efficient point-of-use distiller which can also produce a continuous flow of distilled water, it is necessary to maintain a steady liquid level in the distiller boiler. However, level sensors and controls generally have been located in the boiler, making it difficult to maintain the needed steady liquid level and, in addition, making it even more difficult to clean the boiler. Further, the introduction of cold water into a boiler interrupts vapor production and reduces energy efficiency.
Yet another concern of distilling devices is the evacuation of volatile organic compounds and chemicals (VOC's) that are released during the distillation process. These VOC's, if released in the boiler, can contaminate the distillate. Other problems in the prior art include the fact that some water purification systems produce too much heat, and electric cooling fans tend to be too noisy.
Of great concern today are anticipated government regulations concerning the sanitation of point of use (POU) devices. Sanitation regulation will bring added expense and potential liability to the POU industry. Adding UV upstream and downstream of a reverse osmosis device will not completely eliminate biofilming of RO membranes nor will it match the contaminant removal of distillation. Distillation devices are the least likely to become contaminated; however, sanitation issues still must be properly addressed by facilitating the sanitizing of a distilled water storage reservoir should it become necessary.
Thus, there is a need for a continuous flow water distillation system which is fast and easy to clean and maintain, is energy efficient, incorporates thermal energy recovery, substantially reduces ambient heat, is less noisy, is easy to sanitize, is simple to construct and which is capable of efficient, reliable, and sustainable operation over a long period of time.